Process of concentrating phosphate minerals



Patented Aug. 18, 1942 I PROCESS OF CONCENTRATING PHOSPHATE MINERALS Arthur Crago, Mulberry, Fla., assignor to Phosphate Recovery Corporation, New York, N. Y., a corporation of Delaware 11 Claims.

The present invention relates to concentration of phosphate minerals from their ores.

The methods of concentration which are being extensively practiced for the concentration of phosphate minerals in Florida and elsewhere depend on the useof an agent of the negativeion or anionic active type for preferential collection of the phosphate values in the ore. While phosphate concentrates of commercial grades are obtained by such methods of concentration, they aresometimes obtained with diiilculty and only with the sacrifice of recovery; that is, in the practicing of these methods on a commercial scale, when conditions are so adjusted as to yield high grade concentrates, a considerable percentage of the phosphate values in the ore is often not collected and therefore goes to waste with the tailings.

The general object of the invention is to provide an improved method of concentration which will be economical and practical and which will not only facilitate the production of concentrates oi high grade, but will also result in the recovcry of a high percentage of the phosphate values in the ore.

The invention is the result of the discovery that excellent results asto both grade and recovery may be obtained, with economy,- 'hy flrst subjecting the phosphate ore to a concentrating operation with a negative-ion agent to collect and remove therefrom a'rougher concentrate con taining a high proportion of the phosphate values mixed with some silicious gangue, and thereafter subjecting this rougher concentrate, after removal of the negative-ion agent, to a concentrating operation with a positive-ion agent to collect and remove therefrom most of the contained silicious gangue. The flrst concentrating step of the method can be carried out in such amanner as to collect almost the whole of the phosphate present in the ore but the rough concentrate so obtained will contain a good deal of silica. In recleaning such a rough concentrate by conventional means much of the phosphate accompanies the rejected silica and thereforedoes not appear in the finished concentrate. By submitting the rough concentrates to the second concentrating step of my new process, however,

the silicious impurities removed are accompanied by very little phosphate. Since the rougher concentrates contain very little silica as compared with the original ore, only very small quantitles of positive-ion agent are required. In such small quantities, as I have discovered, the posi- Appllcation October 8, 1940, Serial No. 360,261

standpoint of selectivity without loss in collecting power; that is, it collects almost no phosphate and a very high percentage of the silicious impurities from the rougher concentrate.

By this invention. it is economically possible not only to obtain recoveries, in the form of tinished concentrates, considerably exceeding the recoveries obtained by prior methods of concen-.- tration, but the finished concentrates are of improved grade because of more thorough separation of the impurities in the ore.

In the carrying out of eitherof the two concentrating operations made used bythe invention, any concentrating device may be used which is capable of discharging the collected material in such forms as floating froth, skin or surface float, individual agglomerates, etc. Among such devices are-. included flotation machines and gravity-concentrating tables, the collected mate rial being discharged in the case of the former in the form of a floating froth over the lip of the machine, and in the case of the latter in the form of skin float and suspended a slomerates at the table side.

Examples of negative-ion agents which may be used in the carrying out of the first con-- centrating operation are the higher fatty acids. such as fish oil fatty acid and oleic acid and their soaps, the resin acids and their soaps, wood by-- product fatty acids, naphthenic acids and their salts, the higher sulpho-fatty acids and their salts with the proper bases, the acid esters of high-molecular-weight aliphatic alcohols with inorganic acids and their alkali-metal and alka- 85 line-earth-metal salts, the higher xanthates, etc.

' isoureas and their salts with water-soluble acids,

the resin amines and their salts with water-soluble acids, the higher aliphatic quaternary ammonium bases and their salts with water-soluble acids, the higher alkyl pyrid inium salts of watersoluble acids, the higher alkyl quinolinium salts of water-soluble acids, etc. These various examples of negative-ion and positive-ion agents are not, of course, equally effective or useful in the process of the present invention. The use of an anionic active fatty acid compound is preferred in the carrying out of the first concentrating tive-ion agent gives remarkable results from the operation, while the use of a cationicactive amine compound is preferred in the carrying out of the second concentrating operation.

It is to be understood that the expressions concentrating operation with a negative-ion agent" and concentrating operation with a positive-ion agent are used herein in their broadest sense to include all agents which it may be deemed desirable to employ in the carrying out of these two concentrating operations. The concentrating operation with a negative-ion agent should generally be carried out by employing the negative-ion agent with its usual cooperating substances, namely, mineral oil and alkali. The concentrating operation with a positive-ion agent may be carried out in the absence of additional substances, although the use of mineral oil'along with the positive-ion agent frequently may be found of advantage for the purpose of agglomeration. It may also be desirable in some instances to use the positive-ion agent in a state of solution in an organic solvent. In froth flotation, of course, either of the two concentrating operations suitable frother.

As an intermediate step between the two concentrating operations, 'the process of the present invention includes a removal of the efiect which the negative-ion agent treatment employed in the first concentrating operation would otherwise have on the second concentrating operation carried out by positive-ion agent treatment. This intermediate step particularly aims to remove the eil'ect of the negative-ion agent treatment from the phosphate values recovered in the rougher concentrate, which values otherwise have the tendency to be separated with the remaining impurities in the second concentrating operation; it being understood that this intermediate step not only removes the effect of the negative-ion agent itself, but also removes the eiifect of all other associated agents used in the first concentrating operation. It may, of course, be carried out in various ways, it being sufllcient in most instances to treat the rougher concentrate for a suitable period with a mineral acid, preferably sulphuric acid.

ditioning or preliminary agitation of the rougher concentrate in their presence is required; that is, they may be added directly to the dilute pulp undergoing separation of the remaining impurities.

sisted of two series, namely, a first series of three tests and a second series of two tests. Only the second series of tests should be regarded as being pertinent to the invention, the first series being carried out entirely in accordance with known procedures of concentration by negative-ion agent treatment'to afford a basis of comparison with the second. Each series was'carried out on a sample of minus 35-mesh flotation feed from plant No. 2 of the Phosphate Recovery corporation in Florida, consisting mainly of so-called bone phosphate of lime (tri-calcium phosphate) and silica sand, the B. P. L. (bone phosphate of lime) content of the sample being about 31%.

Tests 1 to 3 Each of these three tests was-carried out as type mixer with flsh oil fatty acid, fuel oil, and

- may be carried out with the additional use of a In preparing the ore for treatment by the proces of the present invention, it is in general desirable that it be comminuted to a particle size most suitable for eflicient operation, and that it be largely deslimed thereby minimizing the consumption of the reagents. ore is first subjected to a preliminary grinding operation and thereafter screened or classified to remove all particles other than those desired. The undersize may then be deslimed, and the oversize reground, deslimed, and added to the deslimed undersize; or the oversize may be reground, added to the undeslimed undersize, and the whole then deslimed.

For a clearer understanding of the invention, certain tests will now be described. These concaustic soda. These three reagents were added during agitation to the mixer, th'eir addition requiring about one minute, after which agitation in the mixer was continued for two more minutes. The pulp conditioned in this manner was transferred to a subaeration flotation machine where, in a diluted state, it was froth'ed for. one minute, during which a rougher concentrate of the phosphate values was floated oil. With the tailing removed, this rougher concentrate was returned to the flotation machine where, without further addition of reagents, it was again treated for a period of one minute to float off a finished concentrate.

The results of the three tests are indicated in v the following table, which gives the reagent quantities employed in each instance in pounds per ton.(2000 lbs.) of dry material treated.

Reagents in lbs. per ton Finished concentrate TestNo.

Fatty Fuel Caustic 5,?- Percent acid 011 sods assay Ins. assay recovery 1.02 2.02 0.70 75.04 a. 12 71.7 0.11 2.03 0.60 75.54 3.51 sac 0.51 1.84 0.50 7&14 3.02 47.3

As will be noted, the reagents in test 1 were employed in the highest amounts, which resulted in a 77.7% B. P. L. recovery in a finished concentrate assaying 75.04% B. P. L. The lesser reagent amounts of test 2 caused an increase of concentrate grade to 75.54% B. P. L., but a drop in B. P. L. recovery to 58.6%. The still lesser reagent amounts of test 3 caused a further increase of concentrate grade to 76.14% B. P. L., but a further drop in B. P, L. recovery to 47.3%. It is clear that the finished concentrate obtained in test 1 was the best obtainable without unduly lowering the recovery. No advantage would have been gained by increasing the reagent amounts used in test 1, which would simply have raised the recovery with a lowering in grade.

' Tests 4 and 5 Each of these two tests was carried out as follows:

In the same manner as before, a rougher concentrate was first produced with fish oil fatty acid, fuel oil, and caustic soda. This rougher concentrate was agitated for two minutes with sulphuric acid to remove the effect of these agents, the contaminated liquor obtained by this acid treatment being removed by decantation. 'The rougher concentrate was then returned to the notation machine where it was formed with water into a dilute pulp of about solids and, without preliminary agitation, frothed for one minute in the presence of octadecylamine acetate. Almost pure silica was floated off in this operation, the material remaining in the machine constituting the finished concentrate.

The results of these two tests are shown in the following table, the reagent amounts being again given in pounds per ton (2000 lbs.) of dry material treated.

ing the ore in aqueous pulp to a concentrating operation in the presence of an anionic active fatty acid compound, a mineral oil and an alkali Reagents in lbs. per ton Finished concentrate Test Rougher float No. #:gg Final Percent Percent Percent meat float B. P. L. Ins my B. P. L. Fatty Fuel Caustic H so amine assay rec.

acid oil soda 4 l. 04 2. 62 0. 70 2. (X) 0. 2) 77. 14 1. 70 79. 2 5 l. 41 3. 60 0. 70 2. (I) 0. ll 77. 14 1.80 87. 5

I Octadecylamine acetate.

This table shows that both tests 4 and 5 resulted in finished concentrates of improved grade and improved recovery. These concentrates were of the same grade, namely, 77.14% B. P. L., but differed greatly in recovery, 79.2% B. P. L. being recovered in the finished concentrate of test 4 and 87.5% B. P. L. being recovered in the finished concentrate of test 5. In this connection it will be noted that, while the reagent quantities used in test 4 for the rougher operation, were substantially the same as in test 1, the fatty acid and fuel oil quantities used in test 5 were appreciably greater than in test 1. Therefore, test 5 started out with a much higher recovery in the rougher concentrate than test 4. Although the rougher concentrate of test 5 was of much lower grade than the rougher concentrate of test 4, yet the finished concentrates of the two tests were of the same improved grade by reason of the very eillcient removal of silica by octadecylamine acetate. This reagent in each of tests 4 and 5 was used in very small amount, and in this small amount had practically no collecting power for the phosphate values in the rougher concentrate. The recovery effected in each instance in the first concentrating operation was consequently maintained in the second concentrating operation.

It is to be understood that the invention as defined in the appended claims is not limited by any details of the foregoing exposition.

What is claimed is:

1. A method of concentrating phosphate minerals from their ores, which comprises subjecting the ore in aqueous pulp to a concentrating operation with a negative-ion agent to separate a rougher concentrate of the phosphate values admixed witth entrained silicious gangue, treating the rougher concentrate with a mineral acid to remove the effect of the negative-ion agent treatment used in its production, and thereafter subjecting the rougher concentrate in aqueous pulp to a concentrating operation with a positive-ion agent which is a selective collector for the gangue in said rougher concentrate to separate a collected material largely composed of the entrained silicious gangue, thereby producing a final phosphate concentrate.

2. A method of concentrating phosphate minerals from their ores, which comprises subjecta collected material largely composed of the entrained silicious gangue, thereby producing a final phosphate concentrate.

3. A method of concentrating phosphate minerals from their ores, which comprises subjecting the ore in aqueous pulp to a concentrating operation in the presence of fish oil fatty acid, fuel oil and caustic soda to separate a collected material consisting of a rougher concentrate of the phosphate values admixed with entrained silicious gangue, treating the rougher concentrate with a mineral acid to remove the effect of the agents used in its production, and sublecting the rougher concentrate in aqueous pulp to a concentrating operation in the presence of octadecylamine acetate to separate a collected material largely composed of the remaining gangue, thereby producing a final phosphate concentrate.

4. A method of concentrating phosphate minerals from their ores, which comprises subjecting the ore in aqueous pulp to a concentrating operation in the presence of oleic acid, fuel oil and caustic soda to separate a collected mate'- rial consisting of a rougher concentrate of the phosphate values admixed with entrained silicious gangue, treating the rougher concentrate with a mineral acid to remove the effect of the agents used in its production, and subjecting the rougher concentrate in aqueous pulp to a concentrating operation in the presence of octa- I decylamine acetate to separate a collected material largely composed of the remaining gangue, thereby producing a final phosphate concentrate.

5. A method of concentrating phosphate minerals from their ores, which comprises subjecting the ore in aqueous pulp to a concentrating operation in the presence of fish oil fatty acid, fuel oil andcaustic soda to separate a collected material consisting of a rougher concentrate of the phosphate values admixed with entrained silicious gangue,'treating the rougher concentrate with sulphuric acid to remove the eflect of the agents used in its production, and subjecting the rougher concentrate in aqueous pulp to a concentrating operation in the presence of octadecylamine acetate to separate a collected material largely composed of the remaining gangue, thereby producing a final phosphate concentrate.

6. A method of concentrating phosphate minerais from their ores, which comprises subjecting the ore in aqueous pulp to a concentrating operation in the presence of wood by-product fatty acid, fuel oil and caustic soda to separate a colhct'ed material consisting oi! a rougher concentrate or the phosphate values admixed with entrained silicious gangue, treating the rougher "'oncentrate with sulphuric acid to remove the effector the agents used in its production, and

subjecting the rougher concentrate in aqueous material consisting of a rougher concentrate of the phosphate values admixed with entrained silicious gangue, treating the rougher concentrate with a mineral acid to remove the effect of the negative-ion agent treatment used in its production, and thereafter subjecting this rougher concentrate in aqueous pulp to a flotation operation with a positive-ion agent which is a selective collector for the gangue in said rougher concentrate to float of! a material largely composed of the entrained silicious gangue, thereby producing a final phosphate concentrate.

. 8. A method of concentrating phosphate'minerals fromtheir ores, which comprises subjecting the ore in aqueous pulp to a tabling operation with a negative-ion agent to effect a table side separation 01 a material consisting of a rougher concentrate of thephosphate values admixed with entrained silicious gangue, treating the rougher concentrate with a mineral, acid-to remove the ei'fect of the negative-ion agent treatment usedin'itsjproduction, and thereafter sub- Jecting this rougher concentrate to a tabling operation with a positive-ion agent whichjis' a selective collectorior the gangue in said'rougher V concentrate" to elect a table side separation of a material largely composed of the entrained silicious gangue, thereby producing a final phosphate concentrate.

9. A method of concentrating phosphate minerals from their ores, which comprises sub]ect ing the ore in aqueous pulp to a concentrating operation with reagents to separate a rougher concentrate of the phosphate values admixed with entrained silicious gangue, treating the rougher concentrate with a mineral acid to remove the eflect of the reagents used in its production, and thereafter subjecting the rougher concentrate in aqueous pulp to a concentrating opcra'tiori to separate a collected material largely composed of the entrained silicious gangue,

thereby producing a final phosphate concentrate.

10'.. A method of concentrating phosphate mineralsi'rom their ores, which comprises subjecting the ore in aqueous pulp to a flotation operation with reagents to float-off a material consisting-mf a rougher concentrate of the phosphate values admixed with entrained silicious gangue, treating the rougher concentrate with a mineral acid to remove the effect of the reagents used in its production, and thereafter subjecting this rougher concentrate in aqueous pulp to a flotation operation to float oil a material largely composed oi the entrained silicious gangue, thereby producing a final phosphate concentrate.

11. A method of concentrating phosphate minerals from their ores, which comprises subjectingthe ore in aqueous pulp to a tabling operation with reagents to effect a table side separation of a material consisting of a rougher concentrate of the phosphate values admixed with entrained silicious gangue, treating the rougher concentrate with a mineral acid to remove the effect of the reagents used inits production, and thereafter subiectingthis rougher concentrate to a tabling operatiori tmeflect a table side separation of a'materiail ilargelycomposed oi the entrained silicious gangi're, thereby producing a final phosphate concentrate.

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